Epinephrine what is it


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Norepinephrine is a catecholamine with multiple roles. It is the hormone and neurotransmitter most responsible for vigilant concentration in contrast to its most-chemically-similar hormone, dopamine, which is most responsible for cognitive alertness. Areas of the body that produce or are affected by norepinephrine are described as noradrenergic. One of the most important functions of norepinephrine is its role as the neurotransmitter released from the sympathetic neurons to affect the heart. An increase in norepinephrine from the sympathetic nervous system increases the rate of contractions in the heart. Norepinephrine also underlies the fight-or-flight response, along with epinephrine, directly increasing heart rate, triggering the release of glucose from energy stores, and increasing blood flow to skeletal muscle. When norepinephrine acts as a drug, it increases blood pressure by increasing vascular tone through α-adrenergic receptor activation. Norepinephrine is synthesized from dopamine by dopamine β-hydroxylase in the secretory granules of the medullary chromaffin cells and is released from the adrenal medulla into the blood as a hormone. It is also a neurotransmitter in the central nervous system and sympathetic nervous system, where it is released from noradrenergic neurons in the locus coeruleus. The actions of norepinephrine are carried out via the binding to adrenergic receptors.

Role of Epinephrine and Norepinephrine in Kidney Function

Epinephrine and norepinephrine are released by the adrenal medulla and nervous system respectively. They are the flight/fight hormones that are released when the body is under extreme stress. During stress, much of the body’s energy is used to combat imminent danger. Kidney function is halted temporarily by epinephrine and norepinephrine. These hormones function by acting directly on the smooth muscles of blood vessels to constrict them. Once the afferent arterioles are constricted, blood flow into the nephrons of the kidneys stops. These hormones go one step further and trigger the renin-angiotensin-aldosterone system, the hormone system that regulates blood pressure and water (fluid) imbalance.

Other Hormonal Controls for Osmoregulation

The renin-angiotensin-aldosterone system (RAAS) stabilizes blood pressure and volume via the kidneys, liver, and adrenal cortex.

Learning Objectives

Describe hormonal control by the renin-angiotensin-aldosterone system

Key Takeaways

Key Points

  • Renin, a hormone produced by the juxtaglomerular apparatus in the kidneys, converts angiotensinogen (which is made in the liver) to angiotensin I.
  • Angiotensin I is then converted to angiotensin II by the angiotensin converting enzyme (ACE), increasing blood pressure by causing vasoconstriction of the blood vessels.
  • Angiotensin II causes the release of aldosterone which is produced by the adrenal cortex; it functions to maintain both sodium and water levels (osmotic balance) in the blood.
  • Angiotensin II also causes the release of antidiuretic hormone (ADH) which functions to conserve water in the body when volume is low; it does this by inserting aquaporins in the collecting duct of the nephron to promote water reabsorption.
  • The atrial natriuretic peptide (ANP) is another hormone that is produced to function as a vasodilator and lower blood pressure by preventing sodium reabsorption.

Key Terms

  • renin: a circulating enzyme released by mammalian kidneys that converts angiotensinogen to angiotensin-I that plays a role in maintaining blood pressure
  • aquaporin: any of a class of proteins that form pores in the membrane of biological cells
  • angiotensin: any of several polypeptides that narrow blood vessels and thus regulate arterial pressure


The renin-angiotensin-aldosterone system (RAAS) is a hormone system that regulates blood pressure and water (fluid) balance. This system proceeds through several steps to produce angiotensin II, which acts to stabilize blood pressure and volume. Renin is secreted by a part of the juxtaglomerular complex and produced by the granular cells of the afferent and efferent arterioles. Renin is a circulating enzyme that acts on angiotensinogen, which is made in the liver, converting it to angiotensin I. Defective renin production can cause a continued decrease in blood pressure and cardiac output. After renin facilitates the production of angiotensis I, angiotensin converting enzyme (ACE) then converts angiotensin I to angiotensin II. Angiotensin II raises blood pressure by constricting blood vessels and also triggers the release of the mineralocorticoid aldosterone from the adrenal cortex. This, in turn, stimulates the renal tubules to reabsorb more sodium. Angiotensin II also triggers the release of anti-diuretic hormone (ADH) from the hypothalamus, leading to water retention in the kidneys. It acts directly on the nephrons, decreasing glomerular filtration rate. Thus, via the RAAS, the kidneys control blood pressure and volume directly. Medically, blood pressure can be controlled by drugs that inhibit ACE (called ACE inhibitors).

Renin-angiotensin-aldosterone system: The renin-angiotensin-aldosterone system increases blood pressure and volume. The hormone ANP has antagonistic effects.


Mineralocorticoids are hormones synthesized by the adrenal cortex that affect osmotic balance. One type of mineralocorticoid, known as aldosterone, regulates sodium levels in the blood. Almost all of the sodium in the blood is reclaimed by the renal tubules under the influence of aldosterone. As sodium is always reabsorbed by active transport and water follows sodium to maintain osmotic balance, aldosterone manages not only sodium levels, but also the water levels in body fluids. Aldosterone also stimulates potassium secretion concurrently with sodium reabsorption. By contrast, absence of aldosterone means that no sodium is reabsorbed in the renal tubules; all of it is excreted in the urine. In addition, the daily dietary potassium load is not secreted; retention of potassium ions (K+) can cause a dangerous increase in plasma K+ concentration. Patients who have Addison’s disease have a failing adrenal cortex and cannot produce aldosterone. They constantly lose sodium in their urine; if the supply is not replenished, the consequences can be fatal.

Antidiurectic Hormone

Antidiuretic hormone or ADH (also called vasopressin) helps the body conserve water when body fluid volume, especially that of blood, is low. It is formed by the hypothalamus, but is stored and released from the posterior pituitary gland. It acts by inserting aquaporins in the collecting ducts, promoting reabsorption of water. ADH also acts as a vasoconstrictor (constricting blood vessels) and increases blood pressure during hemorrhaging.

Atrial Natriuretic Peptide Hormone

The atrial natriuretic peptide (ANP) hormone lowers blood pressure by acting as a vasodilator (dilating or widening blood vessels). It is released by cells in the atrium of the heart in response to high blood pressure and in patients with sleep apnea. ANP affects salt release; because water passively follows salt to maintain osmotic balance, it also has a diuretic effect. ANP also prevents sodium reabsorption by the renal tubules, decreasing water reabsorption (thus acting as a diuretic) and lowering blood pressure. Its actions suppress the actions of aldosterone, ADH, and renin.

Epinephrine Injection

Epinephrine injection comes as a prefilled automatic injection device containing a solution (liquid) and in vials to inject subcutaneously (under the skin) or intramuscularly (into the muscle). It is usually injected as needed at the first sign of a serious allergic reaction. Use epinephrine injection exactly as directed; do not inject it more often or inject more or less of it than prescribed by your doctor.

Ask your doctor or pharmacist to show you and any of your caregivers who could be injecting the medication how to use the prefilled automatic injection device. Training devices are available to practice how to use the automatic injection device during an emergency. Training devices do not contain medication and do not have a needle. Before you use epinephrine injection for the first time, read the patient information that comes with it. This information includes directions for how to use the prefilled automatic injection device. Be sure to ask your pharmacist or doctor if you or your caregivers have any questions about how to inject this medication.

You should inject epinephrine injection as soon as you suspect that you may be experiencing a serious allergic reaction. Signs of a serious allergic reaction include closing of the airways, wheezing, sneezing, hoarseness, hives, itching, swelling, skin redness, fast heartbeat, weak pulse, anxiety, confusion, stomach pain, losing control of urine or bowel movements, faintness, or loss of consciousness. Talk to your doctor about these symptoms and be sure you understand how to tell when you are having a serious allergic reaction and should inject epinephrine.

Keep your automatic injection device with you or available at all times so that you will be able to inject epinephrine quickly when an allergic reaction begins. Be aware of the expiration date stamped on the device and replace the device when this date passes. Look at the solution in the device from time to time. If the solution is discolored or contains particles, call your doctor to get a new injection device.

Epinephrine injection helps to treat serious allergic reactions but does not take the place of medical treatment. Get emergency medical treatment immediately after you inject epinephrine. Rest quietly while you wait for emergency medical treatment.

Most automatic injection devices contain enough solution for one dose of epinephrine. If your symptoms continue or return after the first injection, your doctor may tell you to use a second dose of epinephrine injection with a new injection device. Be sure that you know how to inject the second dose and how to tell whether you should inject a second dose. Only a healthcare provider should give more than 2 injections for a single allergic episode.

Epinephrine should be injected only in the middle of the outer side of the thigh, and can be injected through clothing if necessary in an emergency. If you are injecting epinephrine to a young child who may move during the injection, hold their leg firmly in place and limit the child’s movement before and during the injection. Do not inject epinephrine into the buttocks or any other part of your body such as fingers, hands, or feet or into a vein. Do not put your thumb, fingers, or hand over the needle area of the automatic injection device. If epinephrine is accidently injected into these areas, get emergency medical treatment immediately.

After you inject a dose of epinephrine injection, some solution will remain in the injection device. This is normal and does not mean that you did not receive the full dose. Do not use the extra liquid; dispose of the remaining liquid and device properly. Take the used device with you to the emergency room or ask your doctor, pharmacist, or healthcare provider how to dispose of used injection devices safely.


What should I discuss with my healthcare provider before using epinephrine injection?

Before using epinephrine, tell your doctor if any past use of this medicine caused an allergic reaction to get worse.

Tell your doctor if you have ever had:

  • heart disease or high blood pressure;
  • asthma;
  • Parkinson’s disease;
  • depression or mental illness;
  • a thyroid disorder; or
  • diabetes.

Having an allergic reaction while pregnant or nursing could harm both mother and baby. You may need to use epinephrine during pregnancy or while you are breast-feeding. Seek emergency medical attention right away after using the injection.

In an emergency, you may not be able to tell caregivers if you are pregnant or breast feeding. Make sure any doctor caring for your pregnancy or your baby knows you received this medicine.

How should I use epinephrine injection?

Epinephrine is injected into the skin or muscle of your outer thigh. In an emergency, this injection can be given through your clothing.

Epinephrine is sometimes given as an infusion into a vein. A healthcare provider will give you this type of injection.

The auto-injector device is a disposable single-use system. Follow all directions on your prescription label and read all medication guides or instruction sheets. Use the medicine exactly as directed.

Do not give this medicine to a child without medical advice.

Read and carefully follow any Instructions for Use provided with your medicine. Ask your doctor or pharmacist if you do not understand these instructions.

Do not remove the safety cap until you are ready to use the auto-injector. Never put your fingers over the injector tip after the safety cap has been removed.

To use an epinephrine auto-injector:

  • Form a fist around the auto-injector with the tip pointing down. Pull off the safety cap.
  • Place the tip against the fleshy portion of the outer thigh. You may give the injection directly through clothing. Hold the leg firmly when giving this injection to a child or infant.
  • Push the auto-injector firmly against the thigh to release the needle that injects the dose of epinephrine. Hold the auto-injector in place for 10 seconds after activation.
  • Remove the auto-injector from the thigh and massage the area gently. Carefully re-insert the used device needle-first into the carrying tube. Re-cap the tube and take it with you to the emergency room so that anyone who treats you will know how much epinephrine you have received.
  • Use an auto-injector only one time. Do not try to reinsert an auto-injector a second time if the needle has come out of your skin before the full 10 seconds. If the needle is bent from the first use, it may cause serious injury to your skin.

Seek emergency medical attention after any use of epinephrine. The effects of epinephrine may wear off after 10 or 20 minutes. You will need to receive further treatment and observation.

Do not use epinephrine injection if it has changed colors or has particles in it, or if the expiration date on the label has passed. Call your pharmacist for a new prescription.

Your medicine may also come with a “trainer pen.” The trainer pen contains no medicine and no needle. It is only for non-emergency use to practice giving yourself an epinephrine injection.

Store at room temperature away from moisture, heat, and light. Do not refrigerate or freeze this medication, and do not store it in a car.

What Is Epinephrine?

Allergists recommend that anyone with a serious allergy carry an epinephrine auto-injector with them.

Epinephrine, also known as adrenaline, is a hormone produced by the adrenal glands, which are located on top of each of your kidneys.

The hormone is necessary for maintaining a healthy cardiovascular system — it makes the heart beat more strongly, and diverts blood to tissues during times of stress.

Epinephrine is classified as a catecholamine hormone (as are dopamine and norepinephrine).

Catecholamines are a type of hormone produced by the inner part of the adrenal gland called the medulla.

Emotions such as fear, stress, or anger can trigger the release of epinephrine.

When the hormone enters the bloodstream, the following will increase:

  • Heart rate
  • Cardiac output
  • Blood pressure
  • Sugar metabolism

The above responses help to prepare your body for a “fight or flight” reaction, making you ready for rapid, strenuous activity.

Conditions Affected by Epinephrine

The following health conditions are linked to epinephrine levels:

Addison’s disease is a severe or total deficiency of the hormones made by the adrenal glands, including epinephrine, cortisol, and aldosterone.

Adrenal tumors, some called pheochromocytoma, can cause too much adrenal hormones to be produced. In the case of pheochromocytoma, the hormones produced are epinephrine and noradrenaline.

This over-secretion of epinephrine can lead to a dangerous and severe elevation in blood pressure.

In different types of adrenal tumors, other hormones are over-produced, including cortisol, aldosterone, and androgens.

Epinephrine as Medication

Synthetic epinephrine is also used as a medication for the following:

  • To stimulate the heart during a cardiac arrest
  • As a vasoconstrictor (medication to increase blood pressure in cases of shock)
  • As a bronchodilator and antispasmodic in bronchial asthma
  • To treat a life-threatening condition called anaphylaxis

Anaphylaxis is a severe allergic reaction characterized by a drop in blood pressure and narrowing/swelling of the airways.

It can be caused by insect bites or stings, foods, medications, latex, and many other triggers, depending on a person’s sensitivities.

Epinephrine is the first-response treatment for anaphylaxis. Prescribed by your doctor, it comes as a single dose in an auto-injector (such as an EpiPen).

Allergists recommend carrying an epinephrine auto-injector for serious allergies of almost any kind. Carrying one is especially important if you:

  • Have had a previous anaphylactic reaction
  • Have both food allergies and asthma
  • Are allergic to peanuts, tree nuts, fish, or shellfish

If you’re not sure how serious your allergies are, your doctor can take a thorough medical history and perform blood and skin tests to find this out.

How Epinephrine Works

Epinephrine helps reverse life-threatening symptoms by relaxing the muscles in the airways and tightening the blood vessels.

The medicine is injected into muscles in the thigh during an anaphylactic reaction.

People with a severe allergy should know how to inject epinephrine, as should their family members and people they spend time with regularly.

Ask your allergist or immunologist to show you and your loved ones how to inject epinephrine.

It’s important to note that other medications, such as antihistamines, don’t reverse swelling of the airways or raise low blood pressure, so they won’t help during anaphylaxis.

Epinephrine Side Effects

Common side effects of epinephrine include:

  • Anxiety
  • Restlessness
  • Dizziness
  • Shakiness

Rare but serious side effects of epinephrine include:

  • Abnormal heart rate or rhythm
  • Heart attack
  • Increase in blood pressure
  • Fluid buildup in the lungs

To help evaluate your risk of serious side effects, be sure to tell your allergist about all medical conditions you have.

When a stressful situation occurs and your heart begins to race, your hands begin to sweat, and you start looking for an escape, you have experienced a textbook case of fight-or-flight response. This response stems from the hormone adrenaline. Also called epinephrine, this hormone is a crucial part of the body’s fight-or-flight response, but over-exposure can be damaging to health. Because of this, adrenaline is a hormone worth understanding.

Adrenaline is produced in the medulla in the adrenal glands as well as some of the central nervous system’s neurons. Within a couple of minutes during a stressful situation, adrenaline is quickly released into the blood, sending impulses to organs to create a specific response.

What is the function of adrenaline?

Adrenaline triggers the body’s fight-or-flight response. This reaction causes air passages to dilate to provide the muscles with the oxygen they need to either fight danger or flee. Adrenaline also triggers the blood vessels to contract to re-direct blood toward major muscle groups, including the heart and lungs. The body’s ability to feel pain also decreases as a result of adrenaline, which is why you can continue running from or fighting danger even when injured. Adrenaline causes a noticeable increase in strength and performance, as well as heightened awareness, in stressful times. After the stress has subsided, adrenaline’s effect can last for up to an hour.

Problems associated with adrenaline

Adrenaline is an important part of your body’s ability to survive, but sometimes the body will release the hormone when it is under stress but not facing real danger. This can create feelings of dizziness, light-headedness, and vision changes. Also, adrenaline causes a release of glucose, which a fight-or-flight response would use. When no danger is present, that extra energy has no use, and this can leave the person feeling restless and irritable. Excessively high levels of the hormone due to stress without real danger can cause heart damage, insomnia, and a jittery, nervous feeling.

Medical conditions that cause an overproduction of adrenaline are rare, but can happen. If an individual has tumors on the adrenal glands, for example, he/she may produce too much adrenaline; leading to anxiety, weight loss, palpitations, rapid heartbeat, and high blood pressure. Too little adrenaline rarely occurs, but if it did it would limit the body’s ability to respond properly in stressful situations.

Questions for your doctor

Adrenaline rarely causes problems, but ongoing stress can cause complications associated with adrenaline. Addressing these problems starts with finding healthy ways to deal with stress. Consider asking your doctor:

  • How can I tell if I am dealing with excessive adrenaline?
  • How can I reduce stress in my life?
  • Could adrenaline be causing my symptoms?
  • What affect is adrenaline function and stress having on my overall health?

An endocrinologist is the best type of doctor to talk to when dealing with hormonal issues. Use our helpful form to locate one in your area.

Norepinephrine vs epinephrine: what’s the difference?

Although norepinephrine and epinephrine are structurally related, they have differing effects. Noradrenaline has a more specific action working mainly on alpha receptors to increase and maintain blood pressure whereas epinephrine has more wide-ranging effects. Norepinephrine is continuously released into circulation at low levels while epinephrine is only released during times of stress.

Norepinephrine is also known as noradrenaline. It is both a hormone and the most common neurotransmitter of the sympathetic nervous system. Epinephrine is also known as adrenaline. It is mainly made in the adrenal medulla so acts more like a hormone, although small amounts are made in nerve fibers where it acts as a neurotransmitter.

Norepinephrine Vs epinephrine: Synthesis and Actions in the body

Naturally occurring norepinephrine is mostly made inside nerve axons (the shaft of the nerve), stored inside vesicles (small fluid-filled sacs), then released when an action potential (an electrical impulse) travels down the nerve. Noradrenaline travels across the gap between two nerves where it binds to a receptor on the second nerve and stimulates that nerve to respond. This is norepinephrine acting as a neurotransmitter. Norepinephrine causes vasoconstriction (a narrowing of the blood vessels) so is useful for maintaining blood pressure and increasing it in times of acute stress.

Norepinephrine is also made in the adrenal medulla where it synthesized from dopamine and is released into the blood as a hormone.

Epinephrine is made from norepinephrine inside the adrenal medulla (the inner part of the adrenal gland, a small gland associated with the kidneys). Our adrenal medulla helps us to cope with physical and emotional stress. The synthesis of epinephrine increases during times of stress. Epinephrine acts on almost all body tissues, but its effects are different depending on the tissue, for example, epinephrine relaxes the breathing tubes, allowing easier breathing, but contracts the blood vessels (keeping blood pressure up and ensuring brain and heart are perfused with blood). Epinephrine also increases the heart rate and force of contraction, blood flow to the muscles and brain and aids the conversion of glycogen (a stored form of energy) into glucose in the liver.

Epinephrine diffuses through the adrenal medulla into the blood which perfuses the adrenal glands and is then carried throughout the body.

Norepinephrine Vs epinephrine: Epinephrine has a wider range of effects

Norepinephrine acts mostly on alpha receptors, although it does stimulate beta receptors to a certain degree. One of its most important roles is to increase the rate of contractions of the heart, and together with epinephrine, it underlies the fight-or-flight response.

Epinephrine is relatively nonspecific, stimulating both alpha, beta 1, beta 2, and beta 3 receptors more or less equally. By binding to these receptors epinephrine triggers a number of changes, all of which are aimed at either increasing energy use by the body or making more energy available to be used, for example:

  • Alpha receptors: Insulin secretion by pancreas, glycogen breakdown in the liver and muscle, glycolysis (convert glucose into pyruvate)
  • Beta receptors: Glucagon secretion by the pancreas, increased ACTH secretion by the pituitary gland, increased fat breakdown by adipose tissue.

Norepinephrine Vs epinephrine: Use in medicine

In medicine, norepinephrine is used to increase and maintain blood pressure in acute situations where low blood pressure is a feature (such as cardiac arrest, spinal anesthesia, septicemia, blood transfusions, drug reactions). It is usually used in addition to other agents.

Epinephrine is used in medicine to treat low blood pressure associated with septic shock, for the emergency treatment of allergic reactions, and in eye surgery to maintain dilation of the pupil. It is also available in an autoinjector for people with a history of severe allergic reactions.


In medicine, norepinephrine is used to increase or maintain blood pressure during acute medical situations that cause low blood pressure and epinephrine is used in the emergency treatment of allergic reactions, to treat low blood pressure during septic shock, and in eye surgery to maintain dilation of the pupil.

Epinephrine is mainly produced by the adrenal medulla as a hormone, although small amounts are produced in the nerves and act as a neurotransmitter. Noradrenaline is mainly produced in the nerves, although small amounts are also produced in the adrenal medulla. Both norepinephrine and epinephrine are released during a fight-or-flight response.

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